atomic

For example, an instruction may be said to do several things
"atomically", i.e. all the things are done immediately, and
there is no chance of the instruction being half-completed or
of another being interspersed. Used especially to convey that
an operation cannot be interrupted.

An atomic data type has no internal structure visible to the
program. It can be represented by a flat domain (all
elements are equally defined). Machine integers and
Booleans are two examples.

An atomic database transaction is one which is guaranteed to
complete successfully or not at all. If an error prevents a
partially-performed transaction from proceeding to completion,
it must be "backed out" to prevent the database being left in
an inconsistent state.